4.6 v8 overheating

I have a 1995 4.6 v8 Thunderbird. It runs quarter gauge at idle speed and 2/3 gauge at speeds 60-70 mph. I have replaced the thermostat, still no change. When slow back down it eventually goes back to quarter gauge at idle in gear with A/C running wide open.

you may want to make sure the radiator is clean of debris and backflush it. do you get heat if you turn the heater on? if not you probably have a lack of coolant, or some type of coolant leak.

Check your radiator for obstructions. Bugs and debri can block the fins restricting air flow. Check the radiator for internal blockages. Check oil and coolant levels. If you have an AC condenser in front of the radiator, make sure there is good air flow through the condenser. When was your last oil change? When was the last time the cooling system was flushed? Has the car ever been in a front end colision?

Thanks for the suggestion. I have checked and the coolant level is fine and the cooling system was flushed less than a year ago by the Ford Company. I'm not loosing any coolant. The level is fine. The car can sit in drive with emergency brake on for 2 hours with outside temp 90 degrees and engine runs at normal operating temperature. Just when I drive at 50 mph + is when the temp gauge starts going over half way. When you come back to a stop the needle starts to drop back to normal operating below half gauge.

Oil Change was recent and changed every 4,000 miles. Never been in a collision. Had car 9 years and is in excellent condition. Do you think it is possible the water pump could be going. Water pump is origianl with about 110,000 miles on it.

This is a stupid question but have you checked to make sure the fan kicks on when its hotter? Since they are electric fans it could just not kick in at all and that would be why it could cool when its cooler outside but not when its hotter.

Go by a radiator shop and have them point one of those infrared thermometers at the radiator. If there are cold spots then the radiator is internally clogged restricting the amount of coolant that can be cooled under high demand. Have you checked the radiator fins? If the radiator checks out then I would look at the water pump. It is possible the vanes on the water pump are worn and therefore not circulating enough coolant.